Device for the protection of a vehicle occupant

ABSTRACT

An apparatus for protecting a vehicle occupant that triggers a restraint means as a function of the vehicle occupant&#39;s motion in the context of an accident. The motion is predicted in that by using an occupant detection system and an impact sensor system, a height of the center of mass of the vehicle occupant and a force action on the vehicle occupant are determined, and the motion of the vehicle occupant is thereby predicted.

FIELD OF THE INVENTION

The present invention relates to an apparatus for protecting a vehicleoccupant.

BACKGROUND INFORMATION

German Patent No. DE 42 124 21 describes an apparatus for protecting thevehicle occupant triggers restraint means as a function of theoccupant's estimated motion.

SUMMARY

An example apparatus according to the present invention for protecting avehicle occupant may have the advantage, as compared with the above,that a more exact prediction of the vehicle occupant's motion ispossible. This ultimately results in more optimal triggering of therestraint means. This advantage is achieved by the fact that theoccupant detection system is configured in such a way that it determinesthe height of the traveling center of mass of the vehicle occupant, andfrom that parameter an accurate estimate can then be made regarding theother body data of the vehicle occupant. This results in an accurateprediction as to where the vehicle occupant will be located as afunction of the impact signals.

It is particularly advantageous that the occupant detection system isembodied to determine the seat position of the vehicle occupant, theseat position being taken into account in the motion prediction. If theexact seat position is available, a more accurate prediction of thevehicle occupant's motion is then possible in combination with knowledgeof the center of mass, which provides information regarding the vehicleoccupant's posture.

It is additionally advantageous if the apparatus is connectable to asensor system for sensing a belt pull-out length, the apparatus takingthe belt pull-out length into account in the motion prediction. The beltpull-out length provides information as to how far forward therespective occupant is leaning. This, too, may be an important parameterin determining the vehicle occupant's motion. If the vehicle occupant isalready leaning far forward upon impact, he will then be thrown evenfarther forward by the motion of the impact, so that triggering of afront airbag may in this case be too hazardous because triggering wouldthen strike against the vehicle occupant's head with full force.

It is additionally advantageous if the apparatus determines anupper-body size with the aid of the height of the center of mass and theseat position, and takes the upper-body size into account in the motionprediction. The upper-body size provides an important indication as tohow the vehicle occupant will move under the influence of the impact.Since the upper body is rotated principally about the hip, i.e., aboutthe hip joint, the length of the upper body allows an estimate as to howfar the vehicle occupant's head will move toward the dashboard. This,too, may be an important parameter for accurately predicting the vehicleoccupant's motion.

It is also advantageous if from the forward displacement and the initialseat position, the current seat position during the crash is determined.

Lastly, it is also advantageous if the apparatus has a memory thatencompasses a relationship between the mass of the vehicle occupant andfurther anthropometric data. From the mass, the determination of thecenter of mass, and other directly measured variables, it is possible tocreate an accurate picture of the vehicle occupant's body. This is basedon the fact that given a certain mass and a certain center of mass, itis possible by way of a statistical relationship to draw a conclusion asto the entire body of the person in question. A certain mass and acertain center of mass are associated in highly correlated fashion witha certain body size and also certain body dimensions of the vehicleoccupant's individual limbs. This, too, results in a very accurateprediction of the respective vehicle occupant's motion in the event ofan impact.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention are depicted in thedrawings and will be explained in more detail in the description below.

FIG. 1 is a block diagram of the apparatus according to the presentinvention.

FIG. 2 schematically depicts the apparatus according to the presentinvention.

FIG. 3 is a flow chart.

FIG. 4 is a further flow chart.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the context of the introduction of passenger airbags, the need hasarisen, for reasons having to do with safety and insurance, to detectoccupancy of a passenger seat by a person. In the event of an accidentwith an unoccupied passenger seat there is no occupant to protect, andunnecessary repair costs would arise if the airbag deployed.

Technical solutions exist for seat occupancy detection and for automaticchild-seat detection. With the “smart bags” that are about to beintroduced, greater demands are necessary in terms of detectingoccupancy of the automobile seat. The smart bag is intended to beadaptive to persons and situations in terms of its inflation behavior.

The intention is thus for an intelligent seat occupancy detection systemto exist. Triggering of the passenger airbag should be prevented if, incertain situations, deployment of the airbag would work to theoccupant's disadvantage. This is the case, for example, if a child issitting in the passenger seat or if a person is too close to thedashboard.

According to the present invention, an apparatus for protecting avehicle occupant is proposed that calculates an individual triggeringstrategy in the vehicle and determines an occupant-position-dependenttriggering time of the airbag in the event of an accident, or preventstriggering if the occupant is too close to the dashboard. Presented forthis purpose is a method with which, with the aid of a variety ofsensors, the occupant's forward displacement can be predicted.

In the simplest case, the occupant sensing system—for example anabsolute weight measurement system, a sensor mat, a video sensingsystem, or an ultrasound sensing system—usually yields four signalsregarding the absolute weight measurement, which supply the absoluteweight (in kg) from each sensor. This information can be employed, inaddition to the determination of the center of gravity, for positiondetection. Other seat-based methods, such as the seat mat, canoptionally supply an entire pressure profile. Irrespective of the sensorsystem, however, it is possible by way of the change in motion and theposition of the center of gravity in the X and Y directions to determinethe height of its center of mass. In other words, information existsregarding the occupant's center of gravity in the X, Y, and Zdirections.

Proceeding therefrom, information is additionally available regardingthe occupant's position. Since certain ambiguities in the center ofgravity make it impossible to distinguish unequivocally whether theperson is sitting on the seat or may be leaning extremely far forward,the belt pull-out length and the position of the seat relative to thevehicle, for example, can also be incorporated as correction variables.The position of the seat can be sensed, for example, via a seat positionsensor, or the information is available on the CAN bus. The latter isusually the case with electrically adjustable seats. The occupant'sposition while traveling is thus available.

The apparatus according to the present invention is furthermore capable,based on knowledge of the occupant's position on the respective seats(driver, front passenger, and rear passengers), of determining orpredicting the trajectory and individually adapting the restraint meanson the basis of the respective trajectory. A determination of thetrajectory of each individual occupant makes it possible to adapt therestraint means individually as a function of the trajectory and theparticular accident situation. Optimum protection of the occupant in theevent of an accident is thus obtained. The current position of eachoccupant is sensed with the aid of a sensor, for example a video cameraor weight-based systems. The forces acting on the occupants in the Xand/or Y and/or Z directions are also sensed, for example by way ofacceleration sensors. The individual trajectory can be calculated orpredicted based on a knowledge of the forces acting on the occupant andof the current position of the occupant. The relative velocity withrespect to the vehicle and relative acceleration with respect to thevehicle, derived from the change in the occupant's position over time,can also, for example, be used to calculate the occupant trajectory.With this trajectory calculated individually for each occupant as afunction of the particular accident situation, the restraint means areindividually and optimally triggered. With a knowledge of the locationof the person's head or upper body at each specific moment during anaccident, it is possible to use the restraint means optimally in orderto protect the person. That includes an optimum firing time and acorresponding inflation characteristic in the case of an airbag.

According to the present application, the term “motion” may thus notonly be understood as, for example, the forward displacement of thevehicle occupant, but also as the trajectory, i.e., the motion sequenceof the vehicle occupant in response to forces that occur in an accident.FIG. 1 is a block diagram showing an example apparatus according to thepresent invention. An occupant detection system 1 is connected via adata output to a control unit 2 for restraint means. An impact sensorsystem 3 is connected to control unit 2 via a second data input. Controlunit 2 is connected via a data output to restraint means 4.

Occupant detection system 1 is in this case, in particular,weight-based, i.e., pressure sensors in the seat cushion or forcegauging pins on the seat can be used, or wave-based occupant detectionmeans such as video or ultrasound can be used. This occupant detectionsystem allows determination of the seat position and characterization ofthe person, i.e., an occupant classification. The occupantclassification is performed predominantly on the basis of weight,different classes being defined for which a different inflation behaviorof the airbag is applied. For persons under 45 kg, for example, the useof airbags is not indicated in order to avoid a risk of injury in such acase. Impact sensor system 3 is usually embodied as an inertial sensorsystem. This encompasses, in particular, acceleration sensors that aredisposed in the X, Y and possibly also Z direction in the vehicle. Thissensor system can be placed centrally in control unit 2 itself, but inaddition can also be placed remotely in satellite sensors, e.g., in theB-pillar and/or as up-front sensors that are mounted in the vicinity ofthe vehicle's radiator. Impact sensors 3 also include a pre-crash sensorsystem, i.e., radar or video or ultrasound, which enables monitoring ofthe surroundings. With these sensors it is possible to determine theimpact velocity or the relative velocity between the vehicle and theimpact object. The impact sensors also include deformation sensors orindirect deformation sensors such as pressure and temperature sensors.Control unit 2 is usually mounted on the vehicle tunnel, but can also bedisposed at other locations in the vehicle. As discussed above, controlunit 2 also encompasses its own sensor system that is used either forimpact detection and assessment, or only for plausibility testing ofsignals from remote impact sensors. A combination of plausibilitytesting and impact detection is also possible for a sensor system incontrol unit 2. Restraint means 4 are usually airbags, but restraintmeans 4 can also be understood as belt tensioners, active seats, and/ora roll bar.

FIG. 2 schematically depicts an example apparatus according to thepresent invention. A person 201 is depicted here as a vehicle occupantsitting on a vehicle seat 210. In particular, the person is depictedhere three times in order to represent the sequence during a forwarddisplacement in response to an impact. Person 201 has a center of mass202 that is determined by the occupant detection system. A pressuresensor 205, e.g. a seat mat, is installed in the seat cushion. Forcegauging pins 206 can be disposed in the supports of seat 210 in order todetermine the weight of vehicle occupant 201. Force gauging pins 206also make possible determination of a weight distribution, and thus ananalysis of the seat position. It is furthermore possible to provide aseat position sensor 208 which detects the point at which seat 210 islocated. This can also be retrieved by way of an identifying signal ifan electric seat adjustment system is present. Person 201 is protectedby a seatbelt, on which a belt pull-out length sensor 204 is present inorder to measure the forward displacement of person 201. The beltpull-out length sensor is disposed in B-pillar 203. In an accident,person 201 is usually displaced forward, i.e., toward the dashboardhaving airbag module 209.

The height of center of gravity 202 of a seated person 201 is located atapproximately 25 to 30% of his or her upper-body length. Since theheight of center of gravity 202 is known, the upper-body length can beinferred, for example, using the formula (upper-body length incm)=(center of gravity)/0.275. A memory of control unit 2 can contain areference table by which different body masses, and masses forindividual body parts, can be ascertained from the measured variables.If a table of this kind for different body types is stored in thememory, it is then possible, proceeding from the measured mass of theoccupant, to ascertain the table most relevant to him in terms of massand the height of the center of mass. Alternatively, the reference tablecan be a database designed for human beings, containing mass, body size,mass of the center of gravity, as well as anthropometric data such asthe body dimensions of individual limbs of different persons. Not onlycan plausibility values be derived from this, but the head size can alsobe extracted therefrom. Plausibility could be tested, for example, bythe fact that the calculated upper-body length should correspond to thevalue in the reference table within a certain tolerance range. If so,the head size can be assumed with a certain probability, and it iscorrected if applicable. The calculation of upper-body length and headsize thus provides an indication of the head's current position in thevehicle. In the event of a crash, a double integration of theacceleration signal is performed by the acceleration sensor or thepre-crash sensor. That yields an indication of the distance traveled.From the current position of the occupant and the distance signal, it ispossible to make an estimate of where the occupant will be at time T.

This method therefore makes it possible to determine the occupant'sinitial position before the crash. Starting at the moment of crashcontact, the acceleration signal measured in the central control unit isdoubly integrated. The value of the double integral reflects the forwarddisplacement of an unrestrained mass, and therefore corresponds (to afirst approximation) to the occupant's forward displacement. The valueof this second integral is compared with a threshold that depends bothon the impact velocity and on the occupant's seat position prior to thecrash. It is thus possible, for example, not to fire the airbag if theoccupant is located at or close to the dashboard, to fire the airbagearlier if the occupant is leaning forward in terms of the normalposition, or to fire the airbag later if the occupant is leaning fartherback than normal. It is thus possible to control the triggeringdecision. That triggering decision can encompass, for example, thedecision as to whether to fire the restraint means, and if so at whatlevel and at what point in time. Alternatively, other models for forwarddisplacement calculation can be used; the approach described above usingthe double integral is merely one example of a calculation.

FIG. 3 illustrates execution of an example method according to thepresent invention. In method step 301 the mass of the person isdetermined via occupant detection system 1. In method step 302 the seatposition of vehicle seat 210 is determined. In method step 303 the beltpull-out length is determined with belt pull-out length sensor 204. Inmethod step 304 the acceleration in the X and Y directions isdetermined. From these parameters, the overall mass and the position ofthe center of mass are determined in method step 305. From that, inmethod step 306, the positions of the seat, upper body, and head aredetermined. In method step 308 a plausibility test is performed,specifically using stored body dimensions or a reference table frommethod step 307. These data can be stored, for example, in an EEPROM. Inmethod step 309 a correction is performed if applicable. In method step310 the position in the event of a crash is estimated, based on thecurrent seat position and the forward displacement that was determinedin method step 311 from the signal of the pre-crash sensor oracceleration sensor. A plausibility test is also performed in methodstep 312 by impact sensor system 3, and is conveyed to method step 310.If the plausibility test was passed, the triggering time for therestraint means is then determined by airbag control unit 313, and inmethod step 314 a corresponding triggering of the selected restraintmeans 4 is performed.

FIG. 4 shows, in a flow chart, the steps performed in order to determinethe trajectory of the occupant, i.e., of the moving occupant. In methodstep 401 the acceleration or the forces acting on the occupant and themotor vehicle are determined by sensor system 3. In method step 402 theoccupant's position is determined with the aid of occupant detectionsystem 1. From that, in method step 403, the occupant's trajectory ispredicted. From the acceleration from method step 401, in method step404 the accident situation or accident severity is determined. From theoccupant's trajectory and the accident severity, in method step 405 anindividual activation of restraint means 4 is performed.

1-6. (canceled)
 7. An apparatus for protecting a vehicle occupant,comprising: an arrangement configured to trigger restraint means as afunction of a motion of the vehicle occupant, the arrangement configuredto determine, using an occupant detection system and an impact sensor, aheight of a center of mass of the vehicle occupant and a force action onthe vehicle occupant, and thereby predicts the motion of the vehicleoccupant.
 8. The apparatus as recited in claim 7, wherein the occupantdetection system is configured to determine a seat position of thevehicle occupant, the arrangement taking the seat position into accountin the prediction of the motion.
 9. The apparatus as recited claim 7,wherein the apparatus is connectable to a sensor system for sensing abelt pull-out length, the arrangement taking the belt pull-out lengthinto account in the prediction of the motion.
 10. The apparatus asrecited in claim 8, wherein the arrangement is configured to determinean upper-body size using the height of the center of mass and the seatposition, and takes the upper-body size into account in the predictionof the motion.
 11. The apparatus as recited in claim 10, wherein thearrangement includes a memory that stores a relationship between a massof the vehicle occupant and further anthropometric data.
 12. Theapparatus as recited in claim 7, wherein the arrangement determines theforward displacement by using the impact sensor system, and determines acurrent seat position during the crash using an initial position.